A recent article in Contemporary Topics in Laboratory Animal Science by Pullium and colleagues expressed the opinion that because no other source could be found for a parvoviral contamination detected in sentinel mice prior to deployment, the infection apparently came from the unspecified vendor, even though no antibodies were ever detected in mice within 3 weeks of arrival. As this opinion may be shared by others and expresses some of the deep frustration in trying to detect the source of parvoviral infection in facilities using cage-level bioexclusion housing, Charles River Laboratories (CRL) feels it important to contribute to scientific dialogue by claiming to be the unnamed vendor in the Pullium article and discussing why a parvoviral contamination in a CRL barrier room would be detected rapidly. We show that viral infections in CRL barrier rooms rapidly reach high prevalence and that such contaminations historically have been detected quickly, and we describe why we feel enhancements in current monitoring methods provide for even more rapid detection of parvoviruses. Furthermore, we present substantial evidence that the barrier rooms that served as the source of the customer-suspect sentinel mice remain free of all parvoviruses, in light of monitoring of hundreds of mice by all available techniques. Therefore, although an initial list of all possible sources of contamination prudently should include vendors, the evidence is overwhelming that this vendor was not the source of the parvoviral contamination discussed in the Pullium paper.